1. Field of the Invention
The invention disclosed is broadly related to telecommunications and is more particularly related to systems and methods to provide telephony for cable access networks.
2. Prior Art
Broadband access networks (e.g., hybrid fiber/coaxial) are used to provide television programming and Internet access for customers. More recently they are being investigated to provide IP telephony service. However, the reliability of hybrid fiber/coaxial (HFC) cable networks is not comparable to the high reliability of the local telephone network. Local telephone networks are designed to meet an unavailability objective of 53 minutes/year/line. HFC cable networks have a downtime of 622 minutes/year/line due to AC power failure and additional 125 minutes/year/line due to failures other than AC power failure (e.g., amplifier failure, water leakage, cable cuts). One key difference between a local loop network and an HFC cable network is that the former uses battery power at the central office. The latter requires voltage from the coaxial cable are sources of power for the DC voltage applied to the IP voice circuits. A power outage sensor selectively connects the IP voice circuits to either the AC/DC power converter and regulator in the modem or, alternately, the DC voltage from the coaxial cable, depending on whether there is an outage sensed at the cable data modem. The other circuits such as the video/audio receiver circuits and IP data transceiver circuits are powered only by the AC/DC power converter and regulator in the cable data modem. In this manner, if there is a general power outage affecting both the trunk amplifier and many of the cable data modems connected to it, the power to be supplied by the backup battery at the trunk amplifier is only required to power the IP voice circuits and the subscriber""s telephone hand set. The invention is a cost-effective solution to providing uninterruptible telephone service on an HFC cable network, in the face of power outages anywhere from the cable network headend to the subscriber""s telephone.